1. Field of the Invention
The present invention relates to a lighting circuit. More particularly, the present invention relates to a lighting circuit capable of lighting a vehicular lamp including a light-emitting diode.
2. Description of the Related Art
Conventionally, a switching regulator is known that supplies power to a light source of a vehicular lamp as disclosed, for example, in Japanese Patent Application Laid-Open No. 2001-215913, page 3, FIG. 7.
A vehicle carries high flammable fuel such as gasoline. Thus, the switching regulator mounted on the vehicle should have high safety.
However, in a case where the output of the switching regulator is short-circuited or earthen, for example, the load on the switching regulator increases. Therefore, the switching regulator may break down, emit smoke or generate heat because of burden of excess power.
Moreover, in a case where the output became open because of, for example, breaking, an output voltage may increase excessively in a flyback switching regulator, for example. This may lead to danger of electric shock to a user or risk of leak caused by the excessive high voltage, smoking or firing caused by discharge.